1. Field of the Invention
This invention relates to a novel transition metal crystalline alumino-silicate, a method for its preparation, its use; and to a transition metal-extracted crystalline alumino-silicate, a method for its preparation from the aforesaid transition metal crystalline alumino-silicate and its use as a catalyst, especially for selective dewaxing of hydrocarbon oils.
2. Brief Description of Disclosures in the Art
Zeolite materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversions. Certain zeolitic materials are ordered, porous crystalline alumino-silicates having a definite crystalline structure within which there are a large number of smaller cavities which may be interconnected by a number of channels. These cavities and channels are precisely uniform in size. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline alumino-silicates. These alumino-silicates can be described as a rigid, three-dimensional framework of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms, whereby the ratio of the total aluminum and silicon atoms to oxygen is 1:2. The electrovalence of the tetrahedra-containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca, Sr, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially by another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange it has been possible to vary the properties of a given alumino-silicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic alumino-silicates. These alumino-silicates have come to be designed by letter or other convenient symbols, as illustrated by Zeolite A, U.S. Pat. No. 2,882,243; Zeolite X, U.S. Pat. No. 2,882,244; Zeolite Y, U.S. Pat. No. 3,130,007; Zeolite ZK-5, U.S. Pat. No. 3,247,195; Zeolite ZK-4, U.S. Pat. No. 3,314,752; and Zeolite ZSM-5, U.S. Pat. No. 3,702,886, to name a few.
Prior art techniques have also resulted in the formation of a variety of synthetic transition metal silicates and alumino-silicates, as described in, for example, U.S. Pat. Nos. 4,208,305; 4,376,757; European Patent Application Nos. 0,014,059, 0,013,630, 0,030,751; and U.S. Pat. No. 4,100,262.
A crystalline alumino-silicate zeolite known in the art is offretite. The IOZ-5 zeolite of the present invention resembles offretite in certain aspects of structure, but differs therefrom by having a notably higher silica/alumina ratio, and having associated transition metals incorporated during synthesis. These transition metals impart morphological effects, including particle size range of 0.1-0.25 microns, which further differentiates IOZ-5 from offretite.